I have recently purchased a Stihl BR 400 backpack blower and I have had nothing but trouble out of it. It will sometimes start, and I say sometimes because sometimes it will spit and sputter, then cut off and not start due to flooding. That is my first problem, my second problem happens after I get it started. It runs good for about five or ten minutes then it will start spitting and sputtering and all of a sudden cut off and it wont start back again.

I have emptied all of the gas out of the tank and replaced it with new mix, I have changed spark plugs, but it is still messing up.

Any advice would be greatly appreciated.

topsites

11-10-2009, 11:51 AM

It sounds like the coil / ignition module could be bad.

rotti1968

11-13-2009, 11:49 PM

i would assume you bought this unit used since the 400 has been gone for a while . I would look at the carb, you may have a leaking needle valve. Also i have seen the welch plugs come loose and prevent the needle from closing.If your carb is good then i would lean to the coil/module .
one other note the br 400,420,380,320 were and are known for flooding trying to start them. The procedure should be as follows for starting: when cold set choke turn the kill switch on , pull the recoil "3" times if the unit did not start or bark turn the choke off!!!!, continue to pull the recoil until the unit starts. If the recoil is pulled any more then 3 times with the choke on IT WILL FLOOD. If it does flood, remove the spark plug and dry or replace with a dry plug,make sure the choke is off,pull the the throttle trigger to full throttle and lock with the thumb lock. Now pull the recoil until it starts it may take 5 to 15 pulls but it will start.DO NOT PUT THE CHOKE BACK ON.Once the unit is warm or hot you should not need the choke at all.

tennstripeking

11-16-2009, 06:20 PM

I appreciate your feedback. I still can't seem to find the problem with the blower. I changed the gas again and checked for leaks in the fuel line. I thought that the fuel filter might be clogged, but I can't find a filter in the gas tank. I'm not real familiar with Stihl blowers. (I've always used Redmax). The fuel line goes into the gas tank, but i'm not sure how to replace the filter or if there is one in my tank. Do you think that could be the reason my blower all of a sudden cuts off after several minutes worth of use?

tennstripeking

11-16-2009, 06:22 PM

It sounds like the coil / ignition module could be bad.

Would I be able to tell if the coil is bad by just looking at it? I took it off and cleaned it up, but i'm not sure how I could tell if it is bad. Thanks!

rotti1968

11-16-2009, 06:59 PM

not really any to see if its bad other then doing a spark test with it on the unit. You say you took it off when you reinstalled it did you set the air gap between the coil and the fly wheel? if not get a business card put it between the coil and the fly wheel, loosen the bolts that hold the coil and turn the flywheel until the coil draws to the magnets,tighten the bolts and remove the card. unless you have a spark tester its kind of hard to see what the spark is doing during the run of the unit .
but what you need to do is isolate the coil from the kill circuit to do this simply unplug the wire connections at the coil that go to the kill circuit. Now you have taken the kill switch out of the loop. start the unit if it remains running then you have either bad wiring or kill switch. if it shuts down then you need to go deeper and this is where you should have a spark tester. you need to start the unit with the spark tester connected to the coil and the plug and watch the light to see what happens to the spark when it shuts down, if it goes out and shuts right off get a new coil if it stays lit but shuts down then you have another issue such as fuel etc. I think the coil for the 400 runs about 35.00 or so.

RonAyersMotorsports

11-17-2009, 05:10 PM

When it shuts off is it flooding? OR does it quit firing. Use spark tester after unit shuts off to check fire. Again if its old like already been suggested it could also be carb related. Sounds like you may just need to leave this one to the pro's. Unless you can provide us with more info.

If not take it to your closest dealer.

tennstripeking

11-17-2009, 08:21 PM

It does not cut off due to flooding. It cuts off suddenly in the middle of use (full throttle). Maybe you are right about the keeping it to the pros.

Thanks

mow crew

11-17-2009, 10:10 PM

I'm having the exact problem only mine will not start @ all. I've changed the fuel, plug, air filter, spark arrestor screen, put a carb rebuild kit. I'm going tomorrow to get a fuel filter (which by the way is in the lowest part of the tank right?) I did a compression check and its @ 100+ Then I poured 1/2 teaspoon of oil and got a higher reading probably around 150+/- Does that mean new rings and base gasket? I saw in a older thread to wedge a nickel in the gap of an old plug to look for spark? Can a coil go bad and still have a small amount of spark? Does a coil go bad slowly or stop all @ once? Crap this thing is killing me I've got alot of work tomorrow and only 1 blower...Any help much appreciated!! Also wouldn't it run w/only 100+ of compression?

RonAyersMotorsports

11-18-2009, 09:31 AM

It would run with just 80psi compression. You only need between 75-90psi for combustion to occur. Heres a quick test. Check plug and make sure it is dry. Then remove air filter, and with a spray bottle spray a small amount of gas directly into the carb. Without choking see if unit will attempt to start. If so you still have carburetor problems and need to take it to a professional. If it does not attempt to start. Remove plug and connect to coil while making contact on the engine block and see if you have a good blue spark. If so well take it to a shop I don't think there's much more I can help you with without having the machine in front of me. If not then you may have a coil problem. DON'T put any more oil in the cylinder head. Be sure to clean that crap out before performing these test.

mow crew

11-18-2009, 12:18 PM

I got one running. I then changed the carb from the running unit to the non and no luck. Then just to see I put the non running carb on the good unit and it runs fine. So I guess its the coil? It has really good spark or so it seems. I performed the test you advised for the and it seems to have strong spark and 100+ on compression check. Maybe fuel filter? Crap......Taking it to the shop is NOT an option for me......

rotti1968

11-18-2009, 01:39 PM

[QUOTE=mow crew;3282645] Can a coil go bad and still have a small amount of spark? Does a coil go bad slowly or stop all @ once? QUOTE]

yes you can have weak spark . a coil can god bad all at once,you could have one where you can run the machine for 20 minutes an will die and start right back up and die again.You also can have a problem in the kill circuit,short in the wiring,bad switch. You can loose spark if the plug is not gaped correctly on either the wsr6f or the bpmr7a the gap is .020",you can have a bad ignition lead,boot or spring .

100 psi is more then enough for this unit to run , when you try to start this unit is the plug getting wet ? you may not be getting fuel you could have a pinched line in the tank or bad filter/pickup,or bad fuel lines.Also check to make sure you dont have any water in the fuel tank as this will make it not start or run.

rotti1968

11-18-2009, 01:45 PM

It does not cut off due to flooding. It cuts off suddenly in the middle of use (full throttle). Maybe you are right about the keeping it to the pros.

Thanks

i would go with a coil....

RonAyersMotorsports

11-19-2009, 02:05 PM

I got one running. I then changed the carb from the running unit to the non and no luck. Then just to see I put the non running carb on the good unit and it runs fine. So I guess its the coil? It has really good spark or so it seems. I performed the test you advised for the and it seems to have strong spark and 100+ on compression check. Maybe fuel filter? Crap......Taking it to the shop is NOT an option for me......

Well if this is the case. You need to perform a pressue and leak down test, which I assume you don't have the proper tools to do. Can't help you from here. But please don't assume its the coil from the others up here. You may just start wasting money on a unit that is no good anyway. If your getting fuel, fire, and compression. Well unless it has a leaking seal it should run.

golfandturf

01-07-2010, 12:53 PM

Hi tennstripeking,

Did you have any luck fixing the BR400 as I have one with the same problem, it runs fine for about three minutes then dies as if it's run short of fuel, I've changed the Air Filter, Spark Plug, stripped and cleaned the carb and blown out the fuel filter but all this has made no difference. I am now strongly suspecting the coil but like most people I'm hesitant to spend money without being certain.

Thanks.

mini14

01-09-2010, 11:53 AM

pull the engine cover off, is there oily residue around the carb, residue around the cylinder gasket? if so u have compression probs. buy new gaskets for everything, pull the cylinder off and check its condition and take some sandpaper to clean the top of the piston. r the rings free or stuck....coils generally last a long time. Ive only had 1 go bad in 22 years....just went thru this with a few blowers and they all now run awesome. One reason i dont buy stihl, their replacement parts r $$$$$ and their equipment doesn't last any longer then anyone elses. if u cant get the gaskets right awy u can use the stihl oem sealant called dirko ht, or yamabond 4, or three bond 1194....if u pull the recoil and c a large amount of oil there u could have an oil seal leak, cheap and easy to replace. If the inner oil seal is leaking though it will be a time consuming repair but also very easy.

mcambrose

01-10-2010, 10:14 PM

I had a couple of BR400 blowers which gave me trouble after they had some age. Your problem could be due to a leaking crankshaft seal. If I remember correctly, there is one in front and back of the motor. If the motor heats up the seal may leak air and the engine will die. I had a Shindaiwa that was about 10 years old and it had the same problem. The seals used to not cost very much and were pretty easy to replace. The front one was replaced by removing the pull start and then the nut on the crankshaft. The seal was pulled out with a screwdriver. Good luck.

mini14

01-11-2010, 12:16 AM

be carfull when removing crank seals to not score the shaft, use a screw and screw it into the seal then pull

topsites

01-15-2010, 12:59 AM

I got one running. I then changed the carb from the running unit to the non and no luck. Then just to see I put the non running carb on the good unit and it runs fine. So I guess its the coil? It has really good spark or so it seems. I performed the test you advised for the and it seems to have strong spark and 100+ on compression check. Maybe fuel filter? Crap......Taking it to the shop is NOT an option for me......

Coils going bad in this case would be due to heat...
Sometimes coils work fine when they're cold, then as the engine heats up they crap out.

So, have you tried swapping the coil from the running one to the non?

betmr

01-15-2010, 07:35 AM

Old machines, been sitting with gas in them = Gummed up Carburetor. Carb needs to be taken off and taken apart, and thouroghly cleaned inside, and probably change the reeds.

arska75

02-03-2010, 07:22 AM

Hi, could someone measure the resistance of primary coil, between those thin wires?
Ohter goes to kill switch and other to body.
secondary coil is about 7.4K ohm from spark plug wire to body.
Thanks.

rotti1968

02-03-2010, 09:31 AM

Stihl does not offer any form of resistance testing for the coils. Based mostly on the fact that they are not true coils but modules and have internal chips and circuit boards, you will never get a good reading. Stihl's testing consists of spark or no spark, weak spark or loss of spark when hot, and kill circuit testing. If you isolate the coil and the kill circuit tests good, and your boot and connector are good, then your problem is with your coil and you just replace it.

arska75

02-04-2010, 03:02 AM

okay, first the spark was weak when coil warmed, idle was good. now from coil cames only 30 volts ac. Maybe coil is End of life ;(
I have removed the kil circuit.

tennstripeking

03-11-2010, 06:54 PM

Hey guys just wanted to give yall an update on my br400. I replaced the ignition module and it is working like a champ. I also changed fuel filter, and spark plug. Thanks to all of you for the helping me solve the problem.

arska75

03-14-2010, 03:42 AM

I'm looking used or oem module because in finland original price is about 100$